This is a topographic map of Flattop Mountain, a popular peak near Anchorage, AK. On this map, each red square represents one square mile, and contour intervals are in feet. The red line shows the equivalent volume of the 2009 Redoubt lava dome - 70 million cubic meters. This volume was calculated by USGS geologist Angie Diefenbach at the Cascades Volcano Observatory, using oblique photos taken by AVO geoscientists.
The topographic map is used courtesy of the US Geological Survey. Doug Robbins added the Redoubt volume comparison.
This image may be used, with proper attribution to the U.S. Geological Survey, Doug Robbins, and the Alaska Volcano Observatory.
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